Active magnetic control of a flame

ABSTRACT

A combustion system can allow for the interaction of a magnetic field and an electrical current within a flame supported by a nozzle. The magnetic field can be generated by one or more electromagnets in proximity to or contact with the flame. The electrical current can be generated by a voltage potential difference generated between a first electrode and a second electrode located at tip and base regions of the flame, respectively. The interaction between the electrical current and the magnetic field can generate a force that can produce a constant lateral movement of ions within flame, generating a vortex that can enhance mixing of air and fuel. The speed and direction of this vortex can be controlled by actively varying the magnitude and direction of electrical currents applied in the one or more electromagnets and the electric current induced within the flame, as well as by varying the spatial relationship between these two factors.

The present application claims priority benefit from U.S. Provisional Patent Application No. 61/778,405, entitled “ACTIVE MAGNETIC CONTROL OF A FLAME”, filed Mar. 12, 2013; which, to the extent not inconsistent with the disclosure herein, is incorporated by reference.

SUMMARY

According to an embodiment, a combustion system includes at least two electrodes configured to apply an electrical current through a flame and one or more electromagnets configured to apply a magnetic field to the flame. The flame can be supported by a nozzle configured to dispense a steam of fuel or a mixture of fuel and air into a combustion volume. The electrical current can be generated by a voltage potential difference established between a first electrode and a second electrode, which can be in proximity to or in contact with the flame. According to an embodiment, the electrical current flows through the flame from a tip region of the flame in proximity to or in contact with the first electrode to a base region of the flame in proximity to or in contact with the second electrode. In such a case, a higher voltage potential can be placed on the first electrode and a lower voltage potential can be placed on the second electrode to drive the upstream-flowing current.

In another embodiment, the electrical current flows through the flame from base region of the flame in proximity to or in contact with the second electrode to a tip region of the flame in proximity to or in contact with the first electrode. To make current flow in the same direction as fuel flow, a lower voltage potential can be placed on the first electrode and a higher voltage potential can be placed on the second electrode.

The magnetic field can be generated by a first electromagnet when an electrical current, different from the electrical current flowing through the flame, is applied to it. The magnetic field can have a field strength proportional to the current applied to the first electromagnet and to the number of turns per unit length of a conductive wire forming the electromagnet. Furthermore, the magnetic field can be formed with a polarity that can vary according to the direction of the applied current flow through the first electromagnet.

According to an embodiment, the electrical current generated by the voltage potential applied between the first and the second electrodes and the magnetic field generated by the electric current flowing through the first electromagnet can interact between each other within the flame, producing a force that is perpendicular to both the generated electrical current and the magnetic field. This force can generate a lateral movement on charged particles present in the flame, resulting in a rotational movement of ions interacting with the electric and magnetic fields. Consequently, a vortex can be established in the flame by this rotational movement of ions. A speed and direction of the vortex can be determined by the direction and magnitude of the applied magnetic field and/or by the direction and magnitude of current flow.

In another embodiment, first and second electromagnets driven by first and second electromagnet currents are used together to generate a magnetic field that passes through the flame from one side of the flame to an opposite side of the flame. A north magnetic pole in the crossing magnetic field can be established at the portion of the first electromagnet facing the flame on a first side of the flame, while a corresponding south magnetic pole can be established at the portion of the second electromagnet facing the flame on the opposite (second) side of the flame. When the magnetic field crosses the flame from the first side of the flame to the second side, a lateral force on ions can be maximized because the magnetic field and the current passing through the flame are at a right angle (90°) from each other. In another embodiment, the two electromagnets include magnetic circuit extenders that allow fine-tuning of the magnetic field applied to the flame. A magnetic circuit extender is typically formed from a ferromagnetic core that extends a pole position and/or completes the magnetic circuit.

In yet another embodiment, an elongated solenoid is extended through the flame, wherein a first portion of the solenoid on a first side outside of the flame exhibits a high number of conductor turns, followed by a middle, second portion positioned within the flame that have a lower number of conductor turns, followed by a final, third portion positioned on a second side of the flame opposite the first side that has a high number of conductor turns outside of the flame. When current is applied to the elongated solenoid, a high intensity magnetic field is generated within the flame, which can prevent the flame from propagating upwards.

According to an embodiment, the combustion system disclosed in the present disclosure allows for a suitable interaction of a magnetic field and an electrical current, generating a force that produces a vortex within the flame capable of improving the mixing between fuel and air in the flame, thereby, increasing combustion efficiency and flame stability. In addition, the application of an applied magnetic field is actively controlled by varying the magnitude and direction of the electrical currents applied in one or more electromagnets, thereby controlling the speed and direction of an electromagnetically generated vortex within the flame.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present disclosure are described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. Unless otherwise indicated as representing the background art, the figures represent aspects of embodiments of the present disclosure.

FIG. 1 illustrates an idealized combustion system configured for the application of a magnetic field and an electric current to a flame using one electromagnet and two electrodes, according to an embodiment.

FIGS. 2A and 2B show simplified diagrams that can describe a rotational movement of ions in the flame of the idealized combustion system shown in FIG. 1, according to embodiments.

FIG. 3 shows the idealized combustion system of FIG. 1 with a vortex created by a rotational movement of ions within the flame induced by an interaction between the applied electric and magnetic fields on the flame, according to an embodiment.

FIG. 4 depicts the idealized combustion system of FIG. 1 using two electromagnets disposed at opposite sides of the flame, according to an embodiment.

FIG. 5 illustrates the idealized combustion system of FIG. 1 having an elongated electromagnet disposed to pass through the flame, according to an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, which are not to scale or to proportion, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings and claims, are not meant to be limiting. Other embodiments may be used and/or other changes may be made without departing from the spirit or scope of the present disclosure.

As used herein, the following terms can have the following definitions:

“electrode” can refer to a conducting material configured for the application of a charge, voltage, and/or electric field to a flame.

“electromagnet” can refer to an electrically conducting metal wire configured in one or more loops and capable of generating a magnetic field when an electric current is applied to the one or more loops. An electromagnet can include a ferrous metal core or can be a hollow core (e.g., “air core”) device. A solenoid is a particular type of electromagnet having loops in a helical arrangement.

The present disclosure relates generally to combustion systems, and more particularly, to the application of one or more magnetic fields and electrical currents to a flame within a combustion system.

Magnetic field sources typically employ a combination of permanent magnets and/or electromagnet coils, e.g., tightly wound helixes of conductive wire through which an electric current is passed to generate a magnetic field.

Permanent magnets can be characterized by intrinsic magnetic fields, while electromagnet coils (or solenoids) can generate a magnetic field in response to an applied electrical current.

Application of a charge, voltage or/and electric field to a flame within a combustion system can provide several benefits such as optimization of flame shape and stability, as well as the reduction of combustion byproduct species such as NO_(x) and CO, among others.

Systems for improving combustion efficiency can be limited in terms of the interaction between magnetic components and electrical current. It would be desirable to improve a combustion process by using a system that can effectively combine magnetic fields and electrical currents.

FIG. 1 shows an idealized combustion system 100 configured for the application of a magnetic field B and an electrical current I_(f) to a flame 102, according to an embodiment. A burner 104 is configured to support flame 102 which can be part of a boiler, a water tube boiler, a fire tube boiler, a hot water tank, a furnace, an oven, a flue, a fire tube boiler, a cook top, or the like.

The flame 102 depicted in combustion system 100 can include a plurality of charged and uncharged species. During combustion, charged species such as ions 106 can be produced within flame 102. Such ions 106 can include HCO⁺, C₃H₃ ⁺, H₃O⁺, among others, along with their corresponding but dissociated electrons. Uncharged or neutral species, which can be present, can include uncharged combustion products and byproducts, unburned fuel and air.

A first electrode 108 can apply a voltage V₁ in tip region of flame 102, while a second electrode 110 can apply a voltage V₂ in base region of flame 102. According to one embodiment, V₁ has a lower electrical potential than V₂, producing a voltage potential difference that causes an electric current, I_(f), to flow through flame 102, specifically from the base region to the tip region of the flame 102, as shown in FIG. 1. In another embodiment, V₂ is at a lower electrical potential than V₁, and causes current, I_(f), flow from the tip region to the base region of flame 102. Voltages V₁ and V₂ applied to flame 102 by first electrode 108 and second electrode 110 can vary from about +/−5 kV to about +/−80 kV. As such, current I_(f) intensity can be determined by equation 1 below:

I _(f) =[V ₁ −V ₂ ]/R _(flame),   (1)

where R_(flame) is the electrical resistant of flame 102, which can vary according to flame volume, and/or type of fuel and reactants used during combustion.

First electrode 108 and second electrode 110 can be operatively connected to a voltage power source, where AC or DC voltage can be applied to energize or charge first electrode 108 and second electrode 110. In another embodiment, burner 104 can be electrically charged at applied voltage V₂ to function as second electrode 110 to induce current I_(f) flow through flame 102.

A first electromagnet 112 is placed in proximity to or in contact with flame 102, according to an embodiment. AC or DC current I₁ can be applied to first electromagnet 112, producing, thereby, a magnetic field B that can interact with flame 102. Magnetic field B can be directed towards flame 102 as shown in FIG. 1, with a North magnetic pole facing flame 102. Magnetic field B strength can be proportional to the applied current I₁ and to the number of turns per unit length of first electromagnet 112. According to an embodiment, current I₁ applied to first electromagnet 112 can vary between about 0.1 A to about 100 A, while magnetic field B strength generated by first electromagnet 112 can vary from about 1 μT to about 1 mT. First electromagnet 112 can include suitable conductive materials such as iron, steel (e.g. stainless steel), nickel, cobalt and alloys thereof, and preferably superalloy conductive materials having high temperature resistance such as INCONEL™, HASTELLOY™ and the like.

Although electrodes 108, 110 and first electromagnet 112 are shown in respective shapes and geometric relationships, other geometric relationships and shapes can be contemplated. For example, first electromagnet 112 can include a metal core, while electrodes 108, 110 can be positioned in different regions of flame 102, although such embodiments additionally require thermal shielding or cooling in order to prevent the metal core from exceeding their respective Curie temperatures.

Referring now to FIGS. 2A and 2B, simplified diagrams 200 can describe a rotational movement 202 of ions 106 within flame 102 in combustion system 100 in the presence of an electric and a magnetic field, according to an embodiment. FIG. 2A illustrates the interaction of 1) electrical current I_(f) produced due to the voltage potential differential between V₁ and V₂ and 2) magnetic field B produced by first electromagnet 112 (shown in FIG. 1). The interaction between electrical current I_(f) and magnetic field B can generate a force F that is perpendicular to both the electrical current I_(f) and the magnetic field B.

As shown in FIG. 2B, force F can produce a lateral movement 204 of ions 106, where the constant application of force F can generate a continuous lateral movement 204 of ions 106 that can result in rotational movement 202. The speed of rotational movement 202 of ions 106 can vary according to magnitude of force F which can be at a maximum when angle e between current I_(f), shown in FIG. 1, and magnetic field B is 90° degrees. Conversely, force F can be at a minimum or can exhibit zero magnitude when angle θ between current I_(f) and magnetic field B is 0° degrees,-that is, when current I_(f) and magnetic field B are in parallel.

FIG. 3 shows combustion system 100 with a vortex 302 in flame 102 induced by rotational movement 202 of ions 106, according to an embodiment. Constant rotational movement 202 of ions 106 in flame 102 can generate a vortex 302 in a clockwise direction as shown in FIG. 3. Vortex 302 can enhance the mixing of fuel and air or reactants, improving combustion efficiency in combustion system 100 and contributing to flame stabilization. Furthermore, the rotational speed of vortex 302 can vary according to magnitude of force F which can be proportional to the magnitude of current I_(f) and the magnitude of magnetic field B and can be at its highest level when current I_(f) and magnetic field B are at a right angle or about 90° to one another. In other embodiments, the rotational speed of vortex 302 can vary according to the fuel pressure or the rate at which fuel is dispensed into combustion system 100.

In another embodiment, the direction of vortex 302 in flame 102 can be counterclockwise when current I_(f) flow direction is reversed. For example, current I_(f) flow can be reversed when V₂ is at a lower electrical potential than V₁, thereby inducing current I_(f) flow from the tip to the base of flame 102. In another embodiment, vortex 302 can be counterclockwise when magnetic field B is generated in reverse direction. In such case, current I₁ can be applied on first electromagnet 112 in an opposite direction, establishing a North magnetic pole of magnetic field B on the end of first electromagnet 112 that is not facing flame 102.

FIG. 4 shows combustion system 100 where magnetic field B can be established between first electromagnet 112 and a second electromagnet 402, according to another embodiment. Second electromagnet 402 can have a similar or the same number of turns per unit length as first electromagnet 112 and can be placed in proximity to or in contact with flame 102. In addition to current I₁ being applied to first electromagnet 112, another current I₂ can be applied to second electromagnet 402, establishing a magnetic field B between first electromagnet 112 and second electromagnet 402 as shown in FIG. 4. Furthermore, if both currents I₁ and I₂ are applied in the same direction as is shown, an induced magnetic field B is generated that can flow from a North magnetic pole of first electromagnet 112 to what is established as the South magnetic pole of the second electromagnet 402. The magnitude of magnetic field B can vary according to the magnitude of currents I₁ and I₂, as well as the number of turns per unit length of each of first electromagnet 112 and second electromagnet 402. Similarly, the direction of magnetic field B can vary according to the direction of currents I₁ and I₂ applied to first electromagnet 112 and to second electromagnet 402 provided both currents have the same direction. Moreover, the position of first electromagnet 112 and second electromagnet 402 with respect to flame 102 can be varied. For example, magnetic field B can be applied at either the tip or base regions of flame 102 depending on the position of first electromagnet 112 and second electromagnet 402.

As previously described, magnetic field B generated between first electromagnet 112 and second electromagnet 402 can interact with current I_(f) generated between first electrode 108 and second electrode 110 to produce lateral force F that can induce rotational movement 202 of ions 106, thereby forming vortex 302 within flame 102. As shown in FIG. 4, magnetic field B generated between first electromagnet 112 and second electromagnet 402 can pass through flame 102 and can be perpendicular to current I_(f), which can contribute to achieving maximum lateral force F generation as magnetic field B and current I_(f) can be at right angle or 90°. As such, by actively controlling the magnitude and direction of both currents I₁ and I₂ applied on first electromagnet 112 and second electromagnet 402, the direction and intensity of magnetic field B can be adjusted to modify the speed and direction of vortex 302 within flame 102 according to the desired application.

In order to provide for fine adjustment of the magnetic field B delivered through flame 102, first electromagnet 112 and second electromagnet 402 can also include magnetic circuit extenders. A first magnetic circuit extender can be attached to the North magnetic pole of first electromagnet 112 and a second magnetic circuit extender can be attached to the South magnetic pole of second electromagnet 402. When properly connected, North magnetic pole of first electromagnet 112 and South magnetic pole of second electromagnet 402 can be transferred to the ends of magnetic circuit extenders. These magnetic field extenders can be placed in different regions of flame 102, allowing for fine adjustment of the magnetic field B magnitude delivered through flame 102. According to another embodiment, magnetic circuit extenders can include ferromagnetic materials such as iron, steel, nickel, cobalt, alloys thereof, any alloys of metals such as neodymium and iron, samarium and cobalt as well as some paramagnetic materials such as magnesium, lithium, tantalum, titanium, tungsten and molybdenum. In addition, magnetic circuit extenders can exhibit different geometric shapes and dimensions according to the application. For example, magnetic circuit extenders can exhibit a cylindrical shape with a diameter similar to the diameter used for first electromagnet coil 112 and second electromagnet coil 402.

While FIG. 4 shows combustion system 100 with only two electromagnets, first electromagnet 112 and second electromagnet 402, more than two or a plurality of electromagnets in different configurations can be used to generate a magnetic field B that can interact with current I_(f), and consequently, forming and actively controlling vortex 302 within flame 102.

Referring now to FIG. 5, combustion system 100 can further include an elongated first electromagnet 512 that can pass through flame 102. According to an embodiment, the elongated electromagnet 512 can exhibit a high number of turns in a first section to the left of and outside of flame 102, followed by a lower number of turns in a second, middle section of electromagnet 512 within flame 102, followed by a high number of turns in a third section to the right side of and outside of flame 102. Current I₁ can be applied through electromagnet 512 to generate magnetic field B that can interact with current I_(f). Similarly to previous embodiments, interaction between magnetic field B and current I_(f) can generate a lateral force F that can induce rotational movement 202 of ions 106, forming vortex 302 within flame 102.

The low number of turns in the second or middle section of electromagnet 512 can allow the formation of a stronger magnetic field within flame 102, as shown in FIG. 5, which can prevent flame 102 from propagating upwards. In general, vortex 302 can enhance mixing of fuel and reactants within flame 102, contributing to flame stabilization and flame length reduction.

While various aspects and embodiments have been disclosed herein, other aspects, other embodiments, or combination of disclosed embodiments may be contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

What is claimed is:
 1. An improved combustion system, comprising: a nozzle configured to emit a flow stream including fuel into a combustion volume along a nozzle axis to support a flame; electrodes configured to generate an electrical current through the flame from a first end to a second end; and a magnet configured to generate a magnetic field across the flame; wherein the magnetic field and the electrical current are oriented at an angle to each other.
 2. The improved combustion system of claim 1, wherein the flame carries charged particles.
 3. The improved combustion system of claim 2, wherein the electrodes include at least a first and a second charging electrode.
 4. The improved combustion system of claim 3, wherein the at least first electrode is disposed adjacent to the flame and distal from the nozzle; and wherein the at least second charging electrode is disposed adjacent to the flame and proximate to the nozzle.
 5. The improved combustion system of claim 4, further comprising: a voltage power source in electrical communication with the first charging electrode and in electrical communication with the second charging electrode.
 6. The improved combustion system of claim 5, wherein the voltage power source is configured to be driven by an alternating current (AC) voltage source.
 7. The improved combustion system of claim 5, wherein the voltage power source is configured to apply a first voltage potential V₁ to the first electrode and a second voltage potential V₂ to the second electrode; wherein V₁ and V₂ are different from each other.
 8. The improved combustion system of claim 4, wherein first and second electrodes are configured to produce a voltage potential difference along a length of the flame between a tip region distal from the nozzle and a base region proximate to the nozzle selected to act upon charged particles in the flame to propel the charged particles lengthwise along the flame to generate a current flow through the flame.
 9. The improved combustion system of claim 1, wherein the magnet includes a first electromagnet coil having a first plurality of helical turns wound about a first magnet axis.
 10. The improved combustion system of claim 9, further comprising an electromagnet voltage source operatively coupled to the first electromagnet coil and configured to cause current flow through the first electromagnet coil.
 11. The improved combustion system of claim 10, wherein the electromagnet voltage source is configured to cause the first electromagnet coil to form a first magnetic pole positioned facing the flame; wherein the first magnet axis is positioned at a right angle to the nozzle axis.
 12. The improved combustion system of claim 11, further comprising: a second electromagnet coil defining a second magnet axis; wherein the second electromagnet coil is positioned to form a second magnetic pole facing the flame; wherein the first and second magnet axes are parallel such that first and second magnetic poles are opposite in polarity to form a magnetic field passing through the flame.
 13. The improved combustion system of claim 12, further comprising: first and second magnetic field extenders respectively operatively coupled to the first and second electromagnet coils and configured to couple the magnetic fields generated by the first and second electromagnet coils to the flame.
 14. The improved combustion system of claim 12, wherein the first and second magnet axes are disposed within a plane perpendicular to a direction of the current flow through the flame.
 15. The improved combustion system of claim 9, wherein the first magnet axis is disposed within a plane perpendicular to a direction of current flow through flame.
 16. The improved combustion system of claim 9, wherein the first electromagnet coil comprises a solenoid having a first region having a first number of turns wound about the magnet axis, a second region having a second number of turns less than the first number of turns wound about the magnet axis, and a third region having a third number of turns greater than the second number of turns wound about the magnet axis; wherein the solenoid is supported to pass through the flame such that the second region is centered on the nozzle axis.
 17. The improved combustion system of claim 1, further comprising: a magnetic circuit extender operatively coupled to the first magnetic coil and configured to couple the magnetic field generated by the first magnetic coil to the flame.
 18. A method for providing a vortex within a flame, comprising the steps of: discharging a flow stream including a mixture of fuel and air in a first direction through a nozzle into a combustion volume; igniting the mixture to create a flame including a plurality of charged and uncharged species; generating an electrical current through a length of the flame parallel to the first direction; and generating a magnetic field through the flame oriented at right angle to the first direction and thereby also oriented at right angle to the electric current, wherein the magnetic field interacts with the electrical current to induce a lateral force on the plurality of charged species within the flame resulting rotational movement of the plurality of charged species.
 19. The method for providing a vortex within the flame of claim 18, wherein the plurality of charged and uncharged species further includes a plurality of ions.
 20. The method for providing a vortex within the flame of claim 19, wherein the step of generating an electrical current includes providing at least a first and a second charging electrode.
 21. The method for providing a vortex within the flame of claim 20, wherein the at least first electrode is disposed adjacent to or within the flame and distal from the nozzle, and wherein the at least second charging electrode is disposed adjacent to or within the flame and proximate to the nozzle.
 22. The method for providing a vortex within the flame of claim 21, further includes a voltage power source in electrical communication with the at least first charging electrode and a voltage power source in electrical communication with the at least the second charging electrode.
 23. The method for providing a vortex within the flame of claim 22, wherein the voltage power source is driven by an direct current (DC) or an alternating current (AC) voltage source.
 24. The method for providing a vortex within the flame of claim 22, wherein the voltage power source in electrical communication with the at least first charging electrode applies a first voltage equal to V₁ and the voltage power source in electrical communication with the at least second charging electrode applies a second voltage equal to V₂.
 25. The method for providing a vortex within the flame of claim 24, wherein first voltage V₁ is different than second voltage V₂ thereby producing a voltage potential difference |V₁-V₂| along a length of the flame between a region distal from the nozzle (a tip region) and a region proximate to the nozzle (a base region), wherein the voltage potential difference acts upon the plurality of charged particles to move at least some of the charged particles along the length of the flame and thereby generate a current flow through the length of the flame in a flow direction from the base region to the tip region if V₁<V₂ or from the tip region to the base region if V₁>V₂.
 26. The method for providing a vortex within the flame of claim 25, wherein the step of generating a magnetic field through the flame includes providing at least a first electromagnet coil having a first plurality of helical turns wound about a first magnet axis, the at least first electromagnet coil further having an electric current passing through the first plurality of helical turns from a first end to a second end of the at least first electromagnet coil, wherein the first end of the first electromagnet coil is designated as a South magnetic pole and the second end of the first electromagnet coil designated as a North magnetic pole.
 27. The method for providing a vortex within the flame of claim 26, wherein the North magnetic pole of the at least first electromagnet coil is positioned facing and proximate to or within the flame, wherein the first magnet axis is further positioned at right angle to the nozzle axis.
 28. The improved combustion system of claim 27, wherein the at least first electromagnet coil further includes a magnetic circuit extender attached to the North magnetic pole, the magnetic circuit extender including a ferromagnetic or a paramagnetic metal or alloy core, rod or bar.
 29. The method for providing a vortex within the flame of claim 28, further includes providing a second electromagnet coil having a second plurality of helical turns of a conductor wound about a second magnet axis, wherein a first end of the second electromagnet coil is designated as a South magnetic pole and a second end of the second electromagnet coil is designated as a North magnetic pole when an electric current is passed through the second plurality of helical turns from the first end to the second end of the second electromagnet coil, wherein the second electromagnet coil South magnetic pole is disposed facing and adjacent to or within the flame opposite the at least first electromagnet coil North magnetic pole, wherein the second magnet axis is further positioned at right angle to the nozzle axis.
 30. The method for providing a vortex within the flame of claim 29, wherein the first and second magnet axes are disposed in a collinear relationship.
 31. The improved combustion system of claim 29, wherein the second electromagnet coil may further include a second magnetic circuit extender attached to the second electromagnet coil South magnetic pole including a ferromagnetic or a paramagnetic metal or alloy core, rod or bar.
 32. The improved combustion system of claim 27, wherein the first magnet axis is disposed within a plane perpendicular to a flow direction of the current flow through a length of the flame.
 33. The method for providing a vortex within the flame of claim 27, wherein the first electromagnet coil further includes an elongated helical coil having a first region having a high number of turns wound about the magnet axis, a second region having a lower number of turns wound about the magnet axis, and a third region having a high number of turns wound about the magnet axis, and wherein the elongated helical coil passes through the flame such that the second region is centered within the flame in a plane perpendicular to the flow direction of the current flow within the flame. 